The magnetic properties of sigma phase alloys

Measurements of intrinsic magnetization as a function of temperature and composition have been made on a number of first series sigma phase alloys. In conflict with earlier work, ferromagnetism has been observed in only two systems, Fe Cr and Fe V. The results on Fe Cr exhibit many interesting features, and appear to be consistent with a ferrimagnetic model for these alloys; it is possible, however, that some aspects of the results may be understood on the basis of the collective electron treatment. The Curie points of the Fe Cr alloys vary between 10 and 40°K depending on composition, while the low temperature intrinsic magnetization varies between 4 and 13 EMU g^-1, the rate of variation being about 2 Bohr magnetons per substituted iron atom. The reduced magnetization-temperature curves bear a close resemblance to those observed in ferrites.